WIZnet Developer Forum

Maximum AT+NSEND data block


I am currently working with the Wiz550 S2E module, I am using the module to send QVGA (resolution of 320x240) images to our servers throught an API, the average size of an image is about 300Kbytes. I send 2 images at the same transmission, so the total amount of bytes are about 700Kbytes.

I have achieved to configure the module and send the images without problems, so far is working. My question is about if it is possible to modify the maximum size of the data block with the command AT+NSEND. Empirically, I found that the maximum data block that I can send is 1024Bytes, if I try to send something bigger than that I receive the following error: [F, 4], this error means that the parameter is out of range according to the datasheet.

Sending this amount of data fragmented into blocks of 1024bytes makes the transmission very slow.

I am wondering if It is possible to modify the maximum size of the parameter AT+NSEND or if you found a different solution for a problem similar to mine.

Thanks in advance.


It is possible, but several conditions must be met. and the expandable size will probably be about 2-4kB.

The MCU mounted on wiz550s2e is LPC11E36FHN33 (flash = 96kB, ram = 12kB).
Currently we are using buffers send = 1kB, recieve = 1kB for Ethernet, buffers tx = 1kB and rx = 1kB for serial.

In other words, if you tell me the various conditions you want to work with, I’ll consider customize it.

For example,

  • i don’t need receive in at-command mode.
  • i don’t need use data mode.

And i’m sorry but I do not know any other solution.



Thanks for your reply.

In my application I just send information to our backend systems throught an API, so the only information that I need to retrieve from our servers is the confirmation that the packet has been sent correctly. The total amount of information that I receive is less than 400 bytes.

On this particular application I don’t need to put the module in server mode, I use it as a TCP client for sending that information.

It would be really good to have the possibility to send about 4KB of information.



I will register the contents as an issue in github and try to make the custom firmware.

Please wait.

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